1. Field of the Invention
The present invention relates to a box-shaped structure which is installed outdoors and whose space for installing a cooling apparatus is limited, and which has therein a heating element whose heat generation rate is so large that cooling is required even during the winter season, the box-shaped structure being a box having such a precision control board that the temperature, humidity, dust, and the like affect the performance and life of electronic components. More particularly, the present invention relates to a cooling apparatus therefor and a method of controlling the same.
2. Description of the Related Art
In recent years, advances have been made in production of high-performance electronic components and densification of electronic components on control boards, and the amount of heat generated from the control board has increased remarkably. In consequence, the internal temperature of the box tends to rise, and the assurance of operation and product life of electronic components on the control board are largely affected by the internal temperature of the box. For this reason, it has become impossible to ensure reliability unless the internal temperature of the box is cooled to a fixed level or below.
In addition, due to the adoption of precision electronic components, it has also become an important factor to eliminate moisture and dust in the air inside the box.
Conventionally, to cool this type of box, a method is known in which an indoor unit is installed inside the box and is connected to an outdoor unit outside the box by means of a refrigerant pipe, and such as the one shown in FIG. 20 has been generally adopted.
Hereafter, a description will be given of that heating-element accommodating-box cooling apparatus with reference to FIG. 20.
As shown in the drawing, the following are installed in a box 101: a control board 102 which generates a thermal load; an indoor unit 103; a temperature sensor 104 for detecting the air temperature of the inside of the box 101 and for transmitting a signal to the indoor unit 103; and a power supply 105.
An outdoor unit 106 is installed outside the box 101, and is connected to the indoor unit 103 by means of a refrigerant pipe 107.
In the above-described configuration, if the control board 102 is operated, the internal temperature of the box 101 gradually rises due to its heat generation.
Accordingly, when the temperature detected by the temperature sensor 104 exceeds a set temperature, an operation signal is generated to cause the indoor unit 103 to start operation and, and the internal temperature of the box 101 drops. On the other hand, if the temperature detected by the temperature sensor 104 drops below the set temperature, a stop signal is generated to stop the indoor unit 103.
While repeating the above-described operation, the internal temperature of the box 101 is kept within a fixed range.
With such a conventional heating-element accommodating-box cooling apparatus, since its surrounding portions are sealed by a heat insulating material, heat is not radiated, so that even if the outdoor air temperature is low during such as the winter season, the cooling apparatus must be necessarily operated, so that a large amount of cooling energy is wasted.
An object of the invention is to overcome the above conventional problems, and by installing a cooling apparatus on the panel of the heating-element accommodating box, air inside the box is cooled as heat exchange is effected between outdoor air and air inside the box when the outdoor air temperature is low. Consequently, the operation time of an existing cooling apparatus can be reduced, so that energy saving can be realized. In addition, since the cooling apparatus is mounted exteriorly on the panel, the internal space of the heating-element accommodating box is not used, so that the execution of installation with respect to the existing heating-element accommodating box is easy.
Another object of the invention is to provide a heating-element accommodating-box cooling apparatus which is capable of realizing energy saving and has excellent executionability of installation as described above.
To achieve the above objects, according to the invention, there is provided a heating-element accommodating-box cooling apparatus comprising: an indoor air passage for fetching air in a heating-element accommodating box and returning the air in the heating-element accommodating box to an interior of the heating-element accommodating box to circulate the air in the heating-element accommodating box; an outdoor air passage for fetching outdoor air and exhausting the fetched outdoor air to the outside; a partition plate provided so that both of the air passages become independent of each other; a fan unit for conveying air in the outdoor air passage and the indoor air passage; and a heat exchange element disposed at a point of intersection between the outdoor air passage and the indoor air passage to exchange the sensible heat of the outdoor air and the indoor air, wherein the heating-element accommodating-box cooling apparatus is mounted exteriorly on a panel of the heating-element accommodating box.
According to the invention, when the outdoor air temperature is low, heat exchange is effected between the outdoor air and the air inside the heating-element accommodating box, thereby making it possible to lower the temperature of air inside the box.
Consequently, the operation time of the existing cooling apparatus can be reduced, with the result that it is possible to obtain a heating-element accommodating-box cooling apparatus which is capable of energy saving operation in comparison with a conventional arrangement.
In addition, since the outdoor air and the air inside the heating-element accommodating box do not become mixed, it is possible to avoid the entrance of moisture and dust into the box, so that adverse effects of vapor condensation and dust on the equipment inside the heating-element accommodating box do not occur.
Further, since the heating-element accommodating-box cooling apparatus is mounted exteriorly on the panel of the heating-element accommodating box, the heating-element accommodating-box cooling apparatus can be easily mounted on a heating-element accommodating box which has no extra space.
In addition, as another means, there is provided a heating-element accommodating-box cooling apparatus comprising: a casing having an indoor air inlet and an indoor air outlet which communicate with a heating-element accommodating box as well as an outdoor air inlet and an outdoor air outlet which communicate with outdoor air; and a fan and a heat exchange element provided in the casing, a rotating shaft of the fan unit being arranged in such a manner as to be parallel to a longitudinal direction of the heat exchange element and perpendicular to a blowing-out direction of the indoor air.
According to the invention, by virtue of the above-described means, the casing of the heating-element accommodating-box cooling apparatus can be made thin and compact, and the execution of installation is facilitated.
Also, to achieve the above objects, according to the invention, there is provided a method of controlling a heating-element accommodating-box cooling apparatus including a box air temperature sensor for measuring the temperature of the interior of a heating-element accommodating box, an outdoor air temperature sensor for measuring the temperature of the outdoor air, a fan unit for blowing cool air into the box, an air heat exchange-type air conditioner for cooling the heating-element accommodating box by using air-to-air heat exchange between the air in the box and the outdoor air, and a refrigerant-type air conditioner for the heating-element accommodating box by using a refrigerant, comprising the steps of: operating the air heat exchange-type air conditioner when a temperature difference obtained by subtracting the outdoor air temperature from the box air temperature is greater than a preset temperature difference T1; and operating the refrigerant-type air conditioner when the box air temperature is higher than a preset temperature T2, so as to reduce energy required for cooling the heating-element accommodating box.
According to the invention, by using the above-described means, the air heat exchange-type air conditioner is operated to effect heat exchange between the outdoor air and the air inside the heating-element accommodating box. This lowers the temperature of the air inside the heating-element accommodating box, so that the cooling load is lowered, ad the operating time of the refrigerant-type air conditioner can be reduced. Hence, it becomes possible to reduce the amount of consumption of the energy required for cooling as compared with the conventional cooling operation.